I think that there are two issues here and we are confusing them.

For arguments sake lets say the award you want is 50,000 miles or points or whatever.

You either have to have two accounts with 50,000 points or miles in them or have one account with 100,000 points or miles in it and get the two awards from that account. You can not have one account with 50,001 and one with 49,000 and combine them to get the two awards.

Either each account has to have enough to get it's own ticket, or one account has to have enough to cover both (and I don't believe that there is a program that doesn't let you get two awards from one account people correct me if I'm wrong), you can't combine two on the fly to make up the total.